By design, most EFI Intakes are single plane in the fact that all the runners share a common plenum. Versus each bank of the engine, or half of the opposing firing cylinders, have a seperate plenum. So yes, the L76 is considered a single plane intake. But in the sense of hot rodding, it is not a "conventional" single plane since it does not have a direct path at the cylinder head runner.

 

You da MAN! Thanks!!

 

I have the composite/plastic version of the L76 intake. GMPP makes a carb version for the L92 heads. Which would be better for a max effort drag race application that only high rpms matter? Carb of EFI version?

 

For the best all out high rpm potential, the carb version is your best bet.

 

From an NHRA/IHRA tuner: (Will post link if legal) it isnt a sponsor website.

One of the most oft asked questions is why do carburetors make more power then EFI and why do the car manufacturers use EFI if carburetors make more power?

A few years ago we used some contacts at General Motors to verify some simple facts from some dyno data we had received from a head to head comparison.

An engine was being constructed for Comp Eliminator style racing and the program was going to be electronically fuel injected. Well the system was giving the engine shop some questionable numbers. The shop removed the EFI system and installed some of our Pro Stock carburetors on the EFI manifold top so they could quickly compare systems.

The engine responded immediately with much faster acceleration rates and a 5 percent improvement in power.

The EFI designer was brought out to the site and try as he might he could not out perform those carburetors. When the session wrapped up carburetors were king by 24 horsepower.

I've heard similar stories and similar claims when comparing systems.

So when we analyze this information it really comes down to a simple fact. Carburetors and Electronic Fuel injection are two completely different systems. They share no concepts and each has a different theory.

EFI's claim is this: I will supply sprayed droplets of fuel at the proper air to fuel ratio all the time.

Carburetors claim: I will supply a pre-emulsed froth of fuel and air into the engine at a preset ratio.

The results proved the analysis of the concepts to be correct. In this case, the carburetor was supplying the engine in question with the proper air to fuel ratio, so the EFI's advantage was gone. Remember, EFI has a computer to tune the engine. You have you. If you know how to tune you'll have the advantage. Carburetors (at the risk of sounding chauvinistic) are a man's game. Guessing rarely works. You have to know how to actually tune an engine.

Remember a carburetor is an atomization/emulsion machine. An injection system is a proper air to fuel delivery ratio machine. Two different concepts. If a carburetor can be designed to supply the perfect air to fuel ratio all the time it should consistently outperform EFI. Its design lends itself to have an unfair advantage in atomization.

Obviously adiabatic expansion is the next question on the list. So if we take a good look at the carburetor we see its not only a perfect machine for atomizing fuel, it also has another advantage. The joule-thompson effect.

Tests performed using quartz plates and infra red sensors located in the plenum area beneath an NHRA Pro-Stock engine revealed an intake manifold temperature drop on a 85 degree day of almost 20 degrees as a result of the the carburetor creating this effect.

So when your neighbor with EFI is ingesting 85 degree air, your power-plant could be ingesting 65 degree air.

That's a nice advantage.

But let's not skip over the atomization advantage. In a high end designed carburetor the fuel is emulsed to lift it. Its a controlled froth. I won't kid you, it's very difficult to control. Its much easier to build a carburetor that operates on a vacuum to ratio concept. But the fogging advantage is gone. So when a customer asks, why is this carburetor more expensive than that builders carburetor as they look basically the same. Most of it is all in the emulsion package and the time spent flowing it and tweaking it to do its job. Remember in a high emulsion design .001 of an inch is a big deal. They're difficult to balance and require sophisticated equipment that many shops have never seen. Also, don't go poking things into the metering block passages to inspect them or look around. You might just lose 10 lbs of torque.

The disadvantage of carburetors used to be restriction. I remember back 20 years ago before booster technology really took off you had to size carburetors to operate on 1-2 inches of vacuum in the plenum at the starting line. The restriction alone was probably costing these engines a 2-3 percent power loss.

Tests we performed at Sonny's racing 5 years ago showed us numbers of about .6 in the plenum and spikes of about 1.1 to 1.3 in the runner at the finish-line. That's a pretty huge decrease and just for dynos sake when we built carburetors large enough to reduce this number by on average 40 percent we saw an increase of only about 3-5 horsepower on an IHRA Pro-Stocker. SO that advantage for EFI is now also gone.

Now that these same engines can operate on as little as .5 hg of vacuum at the starting line and only 1-1.2 at the finish-line, the restriction is nil. Really it all comes down to getting the air to fuel ratio correct. If a carburetor can do that, it should win the race every time. After all, by design, it's a superior emulsion machine.

 

93ls1rx7 - good post

 

So you are saying that with a super-tuned carb (the emulsifier explanation) can make more HP than EFI?

 

Thats what he is saying.

 

Carbs used to be better than efi but not anymore at least not compared to the good efi stuff real race cars use. You won't see Carbs on many race cars that aren't required to run them.

 

I realize that the results in GM High Tech showed that the single plane out performed the plastic intake at high RPMs, but it was at SERIOUSLY HIGH RPMS...as in, it got obliterated by the plastic intake until 6800rpms and didnt start pulling away in any useful fashion until over 7200+. I was pretty disappointed at the disparity in torque and horsepower for the first 6500rpms, as I would consider the powerband for my type of application to be in the 5000-7500 range, not the 7500-9000 range. An edlebrock single plane conversion seemed to really help my LT1 setup throughout the powerband, but I would like to run a single plane on my turbo 6.0 too. Are there any other good tests out there with the carb intake on a nastier setup (something big cube or big power adder) to show if it can get out of its own way at all before 6800?

 

I am curious to see those results myself ...
I agree that the carb style intake is not worthwhile unless you will be
running a carb, turning big rpm's, or big boost.
I think the intake will shine at the track with a turbo setup and
a 3,500+ stall, so I am going for it.
Bigger HP street / small tire track cars may benefit from a little less
low end torque in an effort to get traction.